Rotation angle sensor

ABSTRACT

An apparatus for detecting a rotation angle of a rotation around an axis of rotation includes a transducer magnet for generating a magnetic field as well as a plurality of magnetic-field-sensitive sensor elements for detecting the magnetic field. The magnet and the plurality of magnetic-field-sensitive sensor elements are arranged such that, during a rotation around the axis of rotation, the plurality of magnetic-field-sensitive sensor elements circles relative to the transducer magnet around the same. By the plurality of magnetic-field-sensitive sensor elements, a scale is defined, with the transducer magnet being arranged such that the generated magnetic-field comprises a characteristic on a locus on the scale, and the locus on the scale being dependent on a partial area of a full rotation in an unique manner from the rotation angle. The transducer magnet is magnetized inclined to the axis of rotation. The apparatus enables on the one hand a simple transducer magnet structure and on the other hand an accurate and easy measuring processing process.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the detection of rotation angles, suchas e.g. the rotation angle of a throttle flap of a throttle valve. Inparticular, the present invention relates to apparatus or sensors fordetecting rotation angles operating on an analogue magnetic basis.

2. Description of Prior Art

Nowadays, the orientation of a rotary part as an absolute value and/orthe rotation angle, which the rotary part includes with a fixedreference point, is often required for further processing, such as, forexample, a feedback control or similar. These rotatable parts includeboth freely rotatable parts, such as, for example, axes and shafts ofdrives, and parts which are only rotatable in a partial area of the fullcircle, i.e. by less than 360°, such as, for example, rotary regulatorsor throttle flap valves. For measuring the rotation angle varying sensorsystems or arrangements are currently known, which differ from eachother both with respect to their accuracy, their reliability and theirmanufacturing cost. Basically, these sensor types may be organized intotwo different types, i.e. contact systems on the one hand andcontactless systems on the other.

Contact systems are mostly based on a potentio-metric measurement and,due to their simple structure, characterize themselves by very lowmanufacturing costs. However, a great disadvantage of the contactsystems consists in that high temperature drifts result in these systemsand, when vibrations and oscillations occur, such as, for example, in avalve in a motor vehicle, even when the measuring system comprises afixed rotary position, small movements of high frequencies may occur,which may result in a great wearout and in a premature failure of thesystem.

Contactless systems, in turn, can be subdivided into those of the analogand of the digital type. In contactless systems of the digital type, amore complex transducer is required, which logically subdivides thedesired circle area, i.e. the area of possible rotation angles, intoseveral partial segments. A known possibility includes, for example, atransducer structure in the form of a tooth gear or shaft gear which hasa tooth missing at a certain position. Both the “vacancy” and theexisting teeth may be detected by a suitable sensor technology operatingon an optical or magnetic basis, with an angle position being detectedby counting the teeth following the vacancy. Although only a transducerand a sensor are required for this, a disadvantage of this solutionconsists in that the determination of the angle may not be carried outuntil after the first pass or the first detection of the specificallymarked position, i.e. of the missing tooth.

A further prior art realization of a contactless system of a digitaltype includes a complex transducer consisting of several transducerparts as well as one sensor each per transducer part. Each transducerpart subdivides the desired circle area, i.e. the area of possiblerotation angles, into various partial segments. The detection of thepartial segments by the sensors may be carried out optically ormagnetically, for example, via slot metal sheets. When suitablysubdividing the desired circle areas, for example, by halving,quartering, etc. of the same, it may be achieved that the output signalsof all sensors together indicate the value of the rotation angle in adigitally encoded form with a solution of one bit per sensor/transducerpair. For a resolution of approximately 1°, nine bits (512possibilities) have to be encoded, and, as a consequence, ninetransducer components and nine sensors are required for this purpose. Onthe basis of the suitable subdivision into partial segments, the signalis consequently available in digital form without any further A/Cconversion. However, a disadvantage of these solutions consists in thatan increase of the resolution may only be carried out by adding furthertransducer components and sensors. The higher the resolution to beachieved, the more complicated the required transducer is.

Conventionally, contactless analog systems operate with a simple magnetas a transducer and two analog magnetic-field sensors arranged to eachother under 90°. Typically, magneto-resistive (MR) or Hall sensors areused. The transducer magnet is arranged such that its north/south axisruns in a radial direction, such that the magnetic-field sensors outputsignals of a sine and/or cosine course, from which the current rotationangle may be calculated. The resolution will be determined from theaccuracy of the magnetic-field sensors, the environment influences andthe conversion depth of the subsequent analog/digital conversion.Dependent on the arrangements of two sensors under exactly 90°, a greatdeal of labour and time is necessary for realizing this solution, makingit relatively cost intensive.

On the basis of the technical conditions, contactless measurements arefrequently necessary in many fields of applications and are of aconsiderable advantage. On the other hand, these contactlessmeasurements are more complex and thus more expensive. For applicationswith an extremely high number of pieces, manufacturing costs for arotation angle sensor play a very important role. Therefore, there is aneed for a less complex contactlessly measuring rotation angle sensor.

In accordance with DE 3244891 C1, a system for detecting positions withlinear motions is known, in which a simple magnet arranged in directionof the linear motion and a series of sensors arranged equidistantly andparallel to the linear motion, together defining a scale, are used. Thesensors arranged in series detect the magnetic field, with the zerocrossing of the vertical field component, which results from a centrallevel through the magnet, being determined from the measurement, withthe locus of the zero crossing indicating the locus of the magnet.

SUMMARY OF THE INVENTION

The object of the present invention consists in providing an apparatusfor detecting a rotation angle of a rotation around an axis of rotation,which is less complex with comparable measuring qualities.

In accordance with the present invention this is achieved by anapparatus for detecting a rotation angle of a rotation around an axis ofrotation, comprising a transducer magnet for generating a magnetic fieldand a plurality of magnetic-field-sensitive sensor elements fordetecting the magnetic field, with the transducer magnet and theplurality of magnetic-field-sensitive sensor elements being arrangedsuch that, when rotating around the axis of rotation, the plurality ofmagnetic-field-sensitive sensor elements circles around the samerelative to the transducer magnet, and wherein the plurality ofmagnetic-field-sensitive sensor elements define a scale. The transducermagnet are arranged such that the generated magnetic field comprises acharacteristic at a locus on the scale, and the locus on the scaleuniquely depends on the rotary angle at least for a partial area of afull rotation. The transducer magnet is magnetized inclined to the axisof rotation.

The present invention is based on the recognition that thesusceptibility of the potentio-metric systems, the complexity ofcontactless systems of the digital type with respect to the transducerstructure, and the analog/digital conversion in the analog sine/cosinesignal systems may be eliminated in that a transducer magnet and a scaledefined by a plurality of magnetic-field-sensitive sensor elements whichare arranged such to each other that the generated magnetic fieldcomprises a characteristic at one location on the scale and that thelocus on the scale uniquely depends at least for a partial area of afull rotation on the rotation angle. In this manner, it is on the onehand possible to use a simple transducer structure as is for example thecase in the sine/cosine signal systems and to determine, and, on theother hand, to determine the rotation angle position from the measuredmagnetic-field data in a manner which is both simple and may be adaptedto the desired resolution. In contrast to the above-mentionedcontactless systems of the analog type, an inventive sensor and/or aninventive apparatus, for example, does not require any complex sine andcosine multiplier for evaluation, while, at the same time, as comparedto the contactless systems of the digital type, the transducer structuremay be clearly more simple.

The transducer magnet and the plurality of magnetic-field-sensitivesensor elements may be arranged such, that, when rotating around theaxis of rotation, the plurality of magnetic-field-sensitive sensorelements circle around the same relative to the transducer magnet.Expressed differently, either the transducer magnet is fixedly arrangedand the plurality of sensor elements are attached to the axis ofrotation or the transducer magnet is attached to the axis of rotationand the plurality of sensor elements is fixedly arranged such that, whenrotating around the axis of rotation, either the plurality of sensorelements circle around the transducer magnet or the transducer magnetrotates around the axis of rotation, while the plurality of sensorelements is fixedly arranged.

In one embodiment, the transducer magnet is magnetized inclined to or inan angular relationship to the axis of rotation. In this way thetransducer magnet generates a magnetic field comprising a characteristicintersecting the scale defined by the plurality of sensor elements at alocus, which, in the case of rotations within at least one partial areaof the full circle, uniquely depends on the rotation angle. In a specialembodiment, the rotation angle area, for which the locus uniquelydepends on the rotation angle, includes for example an area of 180° or90°.

A clear connection between the locus and the rotation angle in the fullcircle and/or within a rotation angle area spanning 360°, may beachieved, if this is not already the case by the generated magneticfield alone, in that, for example, a further signal is generatedindicating a partial area of the rotation angle of a plurality ofpartial areas of a rotation angle, in which the rotation angle iscurrently located, or, expressed differently, which subdivides therotation angle area into a plurality of partial areas of the rotationangle. By receiving the signal indicating the partial area of therotation angle, clear inferences can be made as regards the rotationangle from a combination from this signal and the locus on the scalewithin the total full circle.

A further possibility for extending the rotation angle area with aunique assignment between the rotation angle and the locus of themagnetic-field characteristic consists in duplicating the plurality ofsensor elements such that a second plurality of sensor elements with thesame function is offset relative to the first plurality of sensorelements by a rotation around the axis of rotation. In this case, acombination of the loci on the first scale and a second scale, which isdefined by the second plurality of sensor elements, in which thegenerated magnetic field comprises the characteristic, uniquely dependson the rotation angle within the total full circle.

The sensor elements may be arranged on a level which is spaced from theaxis of rotation and which is parallel to the same, such that anintegration of the sensor elements into a die, such as for example inthe form of Hall sensors, is possible. In a special embodiment, thesensor elements are arranged in the form of a two-dimensional orone-dimensional array. A preferred arrangement of the sensor elementsincludes a linear arrangement of the same in parallel to the axis ofrotation.

The characteristic comprising the generated magnetic field at the locuson the scale defined by the sensor elements may be a zero crossing, arelative minimum or a relative maximum of a component of the magneticfield in any predetermined direction or the amount of the magneticfield. The loci, at which the magnetic field comprises thecharacteristic, form a geometric extension rotating around the axis ofrotation relative to the sensor elements during a rotation around theaxis of rotation. Within a rotation angle area to be detected, thegeometric extension intersects the scale defined by the sensor elementsat a certain locus. This locus of the magnetic-field characteristic onthe scale uniquely depends on the rotation angle within the rotationangle area to be detected. The locus may be determined from themagnetic-field data of the sensor elements, for example, by means ofinterpolation, while, within the rotation angle area to be detected, aclear inference may be made from the locus on the rotation angle. Inaccordance with a special embodiment, the previously mentionedcharacteristic of the magnetic-field includes, for example, the zerocrossing of the radial component of the magnetic field, with the loci,at which the magnetic field comprises this characteristic, forming anessentially vertical surface to a magnetization direction of thetransducer magnet.

In contrast to conventional sensor systems, an inventive sensor isespecially advantageous in that the sensor part is adapted to beintegrated into a single die, which, for example, may be manufactured ina CMOS standard technology, thereby maintaining manufacturing costs at alow level. In addition, the transducer magnet may be manufactured in amuch simpler and inexpensive manner than is the case with digital angleposition transducer. A high degree of accuracy may be achieved withoutany extremely high resolving analog/digital converters being necessary.In addition, the orientation information and/or the detected rotationangle are immediately available, for example immediately after turningon the sensor, other than is the case in the previously describedcontactless sensor system of the digital type having the missing gear.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be explained indetail below with reference to the attached drawings, in which:

FIG. 1 shows a prospective view of a special embodiment of a rotationangle sensor in accordance with the present invention;

FIG. 2 shows a projection view of the transducer magnet of the sensorfrom FIG. 1 from a line of vision as is indicated by the markers A—A inFIG. 1, and which is perpendicular to the direction of magnetization ofthe transducer magnet;

FIG. 3a shows a graph showing the dependence of the locus of the zerocrossing of the radial component of the magnetic field on the scaledefined by the sensor elements as a function of the rotation angle φ atthe sensor from FIG. 1;

FIG. 3b shows a graph illustrating the course of the radialmagnetic-field strength along the scale formed by the sensor elements inthe illustration shown in FIG. 1; and

FIG. 4 shows a throttle flap valve, in which the sensor from FIG. 1 isused.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

First, reference is made to FIG. 1, which shows a special embodiment fora rotation angle sensor in accordance with the present invention. Therotation angle sensor, which is generally indicated at 10, includes atransducer magnet 20, which is fixedly arranged on an axis of rotation30, as well as a fixedly arranged detector arrangement 40 consisting ofa planar carrier substrate 50 and magnetic-field-sensitive sensorelements arranged thereon and serving as a reference point fordetermining the rotation angle φ of the axis of rotation 30.

The transducer magnet 20 has a cylindrical shape and is attached to theaxis of rotation 30 with its symmetry axis coinciding with the axis ofrotation 30. The transducer magnet 20, as is indicated in FIG. 1 with“S” for the magnetic South Pole and “N” for the magnetic North Pole, ismagnetized along its surface diagonal and/or along a diagonal of arotation surface running in parallel to the drawing level in FIG. 1,with the rotation angle φ being included between the direction ofmagnetization and the reference point of the detector arrangement 40.

In an especially preferred embodiment, as is shown in FIG. 1, theheights of the cylinder-shaped transducer magnets 20 and the diameter ofthe same are selected to be equal. By selecting the dimensions of thetransducer magnets 20 in this way, a high symmetry and an especiallyregular level course are defined, along which the radial component ofthe magnetic-field generated by the transducer magnet 20 is zero andcomprises a zero crossing. The intersection line of the outer jacket ofthe cylindrical transducer magnet 20 with the level in which the radialmagnetic field is zero, is illustrated in FIG. 1 at 70.

In order to illustrate the generation of the intersection line 70, aprojection view of the transducer magnet 20 is indicated in FIG. 2 froma line of vision shown at A—A. In FIG. 2, the direction of magnetizationof the transducer magnets 20 runs in parallel to the projection and/ordrawing level. A line 80 indicates the level, in which the radialcomponent of the magnetic-field generated by the transducer magnet 20 iszero. At 90 a and 90 b two magnetic-field lines of the magnetic-fieldgenerated by the transducer magnets 20 are exemplarily shown, which, ascan be seen from FIG. 2, vertically intersect the level 80, which is whythe radial component of the magnetic-field is zero at the points ofintersection of the magnetic-field lines 90 a and 90 b with the level80.

Turning once more to FIG. 1, the carrier substrate 50 is spaced from thetransducer magnet 20 and from the axis of rotation 30 and fixedlyarranged in parallel to the same, with the magnetic-field-sensitivesensor elements 60 being linearity arranged on the carrier substrate 50,so as to extend themselves in parallel to the axis of rotation 30, andbeing arranged such so as to detect the radial component of thegenerated magnetic-field. Moreover, the magnetic-field-sensitive sensorelements are arranged at fixed distances to each other, so as to definea scale running through the same and in parallel to the axis of rotation30. In the embodiment shown in FIG. 1, the sensor elements are arrangedequidistantly to each other.

In a preferred embodiment, the detector arrangement 40 is integratedwithin a single die, which includes Hall sensors as themagnetic-field-sensitive sensor elements and within which an evaluationcircuit 100 may be additionally integrated, which carries out theevaluation of the sensor signals of the sensor elements explained below.

In one realization of the sensor shown in FIG. 1, Hall sensors arearranged in a linear arrangement in the die 50 asmagnetic-field-sensitive sensor elements, with the same being integratedonto the semiconductor chip at a distance of 151.2 μm among each other,and with the die being positioned with respect to the axis of rotationsuch that the Hall sensors measure the radial field from the transducermagnet with respect to the axis of rotation and the series of Hallsensors are along the axis. In this realization, the diameter of thetransducer magnet is 4 mm and the height of the same is also 4 mm.

After describing the structure of the sensor from FIG. 1 herein above,the functionality of the same will be described below, it beingexplained at first, how the locus of the radial zero-field crossing maybe determined from the measuring values of the sensor elements of thedetector arrangement.

As is shown in FIG. 1, the detector arrangement 40 is near thetransducer magnet 20. As may also be seen, in the rotation angleposition φ shown in FIG. 1, the level of the radial zero-field crossingof the magnetic-field generated by the transducer magnet 20, whichintersects the outer jacket of the transducer magnet 20 at the line ofintersection 70, passes inclined to the scale through a sensor element60 a. As a consequence, the radial magnetic-field detected by the sensorelement 60 a is zero. In addition, the sensor elements arranged abovethe sensor element 60 detect a radial magnetic-field which is oppositeto the one, which is arranged below the sensor element 60 a.

These facts are illustrated in FIG. 3b. FIG. 3b shows a graph, in whichthe x-axis corresponds the scale defined by the sensor element 60 (FIG.1), and along the y-axis the radial magnetic-field strength is plottedin arbitrary units. The measuring points represent the magnetic-fieldstrength detected by the sensor elements in a radial direction. Themeasuring value or the measuring point 110 is for example the measuringvalue detected by the sensor element 60 a (FIG. 1) for the radialmagnetic-field strength, which, as has been already mentioned, is zeroin the sensor element 60 a in the rotation angle position of thetransducer magnet shown in FIG. 1. In addition, the radial component ofthe generated magnetic-field comprises an opposing direction and/or adifferent sign in the sensor elements arranged further above and furtherbelow adjacent to the sensor elements 60 a. In the present case, thelocus of the radial zero-field crossing corresponds to the locus of thesensor element 60 a on the scale.

In the general case, where the zero crossing of the radialmagnetic-field strength does not coincide with the locus of amagnetic-field-sensitive sensor elements, the locus of the zero crossingalong the scale defined by the sensor elements may, for example, bedetermined by means of interpolation, with the zero crossing of theresulting interpolation curve indicating the locus of the zero crossingof the radial magnetic-field on the scale. The curve 120 illustrates,for example, a least-square error fit using a polynomial of apredetermined order, which is achieved using all the measuring values.The interpolation, however, may also be carried out in a differentmanner, such as, for example, by a section-wise polynomialinterpolation, such as for example a section-wise linear interpolation.By means of the interpolation, the zero crossing locus may be determinedwith much higher accuracy than the distance between themagnetic-field-sensitive sensor elements.

For further details with respect to the interpolation and therealization of the same for determining the locus of the zero crossingof the radial magnetic-field on the scale, reference is made to thedocument DE 3244891 C2, which is incorporated herein by reference, andto the Insafa system of the Fraunhofer Gesellschaft. The locus of thezero crossing, however, might be determined by a different method, suchas, for example, by a neuronal network which uses all or a part of themeasuring values as input values.

As will be explained in detail below, inferences may be made as regardsthe rotation angle from the determined locus along the scale. For thispurpose, reference is first made to FIG. 1. During a rotation of thetransducer magnet 20, the magnetic-field rotates together with thetransducer magnet 20, which has been generated by the same, as well asthe level, on which the radial component of the magnetic-field is zeroand which is illustrated by the intersection line 70. In the case that arotation of the transducer magnet 20 around the axis of rotation 30takes place in the direction indicated by arrow 130 from FIG. 1, thelocus of the zero crossing shifts upwards along the scale in an axialdirection. In the case of a reverse rotation, the locus of the zerocrossing shifts downwards on the scale defined by the sensor elements ina reverse axial direction. From the resulting shifting of the locus ofthe zero crossing along and on the scale, there will be a change of themagnetic-field strengths detected by the sensor elements in a radialdirection, from which the rotation angle may be calculated as will bedescribed below.

FIG. 3a shows a graph in which the rotation angle φ on the x-axis andthe locus of the zero crossing on the y-axis on the scale is plotted inarbitrary units. The rotation angle shown in FIG. 1 has been arbitrarilyassigned the rotation angle 90° in FIG. 3b. As can be seen from FIG. 3a,when rotating the transducer magnet 20 around the axis of rotation 30(FIG. 1), the course of the locus of the zero crossing of the radialmagnetic-field along the scale defined by the sensor elements, which isindicated at 140, will result. Therefore, the course 140 represents theconnection between the determined locus on the scale and the rotationangle. As may also be seen, the course 140 in the area from 0 to 180° isstrictly monotonous, meaning that the locus of the zero crossing of theradial component of the magnetic-field generated by the transducermagnet is uniquely dependent on the rotation angle. As a consequence,after determining the locus of the zero crossing on the scale using thecourse 140, inferences may be made as regards the rotation angle φ. Ifthe course shown in FIG. 3b is for example present in analytical form,the rotation angle may be determined from the determined locus on thescale, for example by calculation. If the course 140 is available in asampled or stored form in a look-up table, the rotation angle may bedetermined by quantizing the determined locus on a scale and subsequentlooking up by using the quantized value as an index.

The determination of the locus of the zero crossing on the scale definedby the sensor elements explained with reference to FIG. 3b and theinference as regards the rotation angle φ, which was described withreference to FIG. 3a, using the determined locus may, for example, beimplemented in a hardware and are preferably integrated within theevaluation circuit 100 (FIG. 1), such that both the sensor elements andthe evaluation circuit may be integrated on a single die 50. In apreferred embodiment, the die 50 has been manufactured in CMOS standardtechnology, with Hall sensors as magnetic-field-sensitive sensorelements in addition to the evaluation circuit 100 being integratedwithin the same.

As has been described with reference to FIG. 3a, from the known courseof the locus of the zero crossing of the radial component of themagnetic-field as a function of the absolute rotation angle, therotation angle may be uniquely determined at least for a rotation anglearea of 0 to 180° from the locus determined on the scale. For uniquelydetermining the rotation angle from the determined locus on the scalebeyond the total full circle, additional information is necessary, sincethe course shown in FIG. 3a repeats itself for the rotation angle areafrom 180 to 360°. The resulting ambiguity may be overcome by anadditional digital encoding and/or by subdividing the partial areas,such as, for example, by magnets additionally attached to the axis ofrotation. A radially magnetized magnet may be used, for example, so asto generate a binary signal and/or a magnetic-field indicating the areasfrom 0° to 180° and/or from 180° to 360° and making the samedistinguishable. An alternative embodiment for overcoming the ambiguityof the mapping between the locus of the zero crossing of the scale andthe rotation angle provides, instead of the one-dimensional sensorelement arrangement, as is shown in FIG. 1, a two-dimensionalarrangement of the magnetic-field sensitive and/or magnetic-fieldsensitive sensor elements which provide the necessary information via anadditional analogous evaluation of the measured magnetic-field, such as,for example, by a second evaluation circuit, using an offset angle foreliminating the ambiguity. The sensor elements may for example bearranged in a two-dimensional array, through which, in adjacent columnsrunning in parallel to the axis of rotation, two scales arranged underan offset angle may be defined. Similarly, it is possible to provide asecond detector arrangement offset from the first detector arrangementshown in FIG. 1 by a rotation around the axis of rotation, whichdetermines the second locus on a second scale, with the determined twoloci together uniquely determining the rotation angle on the total fullcircle.

With the rotation angle sensor described with reference to FIGS. 1 to 3a and 3 b, the achievable accuracy by interpolation is 12 bit or ismore, related to a rotation angle area of 180°. The detected absoluteangle values will be made available in digital form. An advantage of thesystem consists in that the orientation values and/or angle values areimmediately available after putting the sensor into operation and,therefore, a rotation until reaching a specifically marked spot, as isthe case in the previously described contactless sensor of the digitaltype with a gear having a missing tooth, is not necessary. By usingseveral sensors, an accuracy can be reached, which is much higher thanthe digital conversion of an individual analog sensor signal of a sensorelement. The accuracy of the sensor may be increased by decreasing thedistance of the sensor elements, without having to make any changes tothe electronic wiring scheme, such as, for example, the resolution ofthe analog/digital conversion, as a result of which advantages asregards the manufacture and/or redevelopment or further development ofthe sensors will result. In addition, the sensor works on a contactlessbasis and is therefore not subjected to mechanical wear. Due to the factthat a certain characteristic of the transducer magnet, typically thezero crossing of the radial field, is used, the arrangement is veryinsensitive towards changes of the absolute magnetic field or thesensitivity of the sensitive elements, which may not be totally avoidedwithin the framework of temperature changes.

In addition, the evaluation part and the detector part may together beintegrated within a single die, as a result of which, in particular withvery high numbers of pieces during manufacture, a highly optimizedmanufacturing process may be achieved.

An exemplary application for an inventive rotation angle sensor is theposition of the throttle flap in a fluid tubing. The angle areaoccurring here overspans 90°. Given a current realization of theinventive sensor, a resolution of approximately 0.05 to 0.1° may beexpected.

FIG. 4 shows the sensor from FIG. 1, as it is used for detecting theposition of a throttle flap in a tubing. FIG. 4 shows a tubing 200, athrottle flap 210, which may rotate in a rotation angle area from 0 to90°, a rotation angle sensor 230, such as the one from FIG. 1, anadjustment means 230, which is merely exemplarily illustrated as a leverin FIG. 4, as well as an axis of rotation 240 fixedly connecting thetransducer magnet of the sensor 220 to the throttle flap 210. Theposition of the throttle flap 210 shown in FIG. 4 corresponds to aclosed position, in which a gas flow or liquid flow 250 in the tubing200 is blocked. By adjusting the throttle flap 210 by means of theadjustment means 230, as is illustrated by a double arrow 260, thethrottle flap may be rotated by as much as 90° so as to enable the fluidflow 250. Via a digital bus 270 for data transmission to, for example, acomputer or any other control means, the sensor 220 outputs in digitalform the current absolute rotation angle φ, which has been determinedfrom the position of the zero crossing of the radial field of themagnetic field generated by the transducer magnet on the scale definedby the sensor elements of the detecting unit. Without any furtheranalog/digital conversion, the absolute angle value may consequently beforwarded as a digital measuring value via the bus 270, such as, forexample, a CAN bus, to a motor control device (not shown).

An exemplary use of the throttle flap shown in FIG. 1 is for example anintake stroke of an internal combustion engine, with oscillations andvibrations becoming apparent, resulting in little highly frequentmotions in potentio-metric solutions with a fixed angle position, whichwould damage a system operating on the basis of contacts. For use in thefield of automative technology the life expectation of the system,however, has to be 12 years or more. In the vehicles trunk, highrequirements are to be made to the temperature area. Resistancemeasurements are frequently flawed with high temperature drifts, suchthat the achievable angle accuracy becomes limited. Furthermore, theprice pressure in this market segment is especially high, as a result ofwhich the above-described cost-intensive contactless solutions areexcluded even in view of their technical advantages.

Here, the use of an inventive sensor, as has been described withreference to FIG. 1, offers an enormous advantage. By using theinventive rotation angle sensor, a realization of the detectorarrangement is enabled, in which the sensor elements together with anevaluation part may be integrated within one single die, which may forexample be manufactured in CMOS standard technology. As a result ofthis, a possibly small surface is enabled. For the transducer no digitalencoding of the angular positions is required. Although the signaltransducer is somewhat more complex than for the magnetic encoding ofsine/cosine signal systems, high accuracy is to be achieved given a morereduced measuring value processing time. In addition, the orientationinformation will be available immediately after turning on the rotationangle sensor and it is not necessary to wait until a certain significantposition, such as, for example, a gear having a missing tooth, has beenreached, until calculating the rotation angle and/or the orientationinformation becomes possible. In addition, an application for greattemperature areas, as they occur in engines, is conceivable. For usewith high temperatures, special substrates, such as, for example, SOIsubstrates (SOI=silicon on insulator) may be used for manufacturing thedetector chip. In addition, the embodiment illustrated in FIG. 1 offersthe advantage that only little temperature drifts occur in rotationangle determination, since the change of sensitivity of the sensors andthe magnetic field are not directly entered into the measurementresults.

With reference to the above-described special embodiment of a rotationangle sensor, reference is made to the following. Although a specialmagnetic transducer structure have been described above, other magneticstructures are further possible. For example, all magnetic transducerstructures are possible, which, for an rotation angle area of interest,map a special characteristic of the magnetic field onto the scaledefined by the sensor elements and in which the locus, onto which thecharacteristic is mapped, uniquely depends on the momentary rotationangle within the rotation angle area of interest.

Further, it should be appreciated, that, although it has already beendescribed above, that the rotation angle for all occurring rotationangles uniquely originates from the locus of the zero crossing on thescale, it may be possible in special applications that the uniqueness isonly required in a partial area, while for the total area of occurringrotation angles an ambiguity is not disturbing. In the applicationexample from FIG. 4, the absolute angle value output by the rotationangle sensor indicates the rotation angle for example by an angleincluding the magnetization direction with a radial connection linebetween the detector arrangement and the axis of rotation, with 0°corresponding to the open position. If now the throttle flap can be alsorotated beyond the area of 0° to 90° on the total full circle, in thiscase of application the ambiguity of an angle measurement may betolerated, since, owing to the symmetry of the arrangement from FIG. 4,it is not significant for the fluid flow whether the throttle flap is inan rotation angle position of 30° or 330°.

With respect to the detector arrangement, it should be appreciated, thatthe sensor elements may also be arranged in a two-dimensional array. Inthe case of a linear arrangement of the sensor elements, it is furthernot required that the sensor elements are arranged in parallel to theaxis of rotation. Although an arrangement of the sensor elements on acommon level is preferred, it is further possible, that the sensorelements are arranged along a curved line, as a result of which a curvedscale is defined. In the case of a flat arrangement of the sensorelements, the scale defined by the sensor elements corresponds to acurved or planar surface.

It should be further appreciated that, although it has been describedabove, the evaluation of the measuring values of themagnetic-field-sensitive sensor elements is carried out in an evaluationcircuit, which is fixedly integrated within the same as are the sensorelements, it is further possible, that the data may be evaluatedelsewhere, such as for example in a computer, an ASIC or a PLA bysoftware, firmware or hardware, in which case the measuring values areoutput in an analogous form, for example by means of a flat band cableor printed circuit board.

Instead of the previously used zero crossing of the radial component ofthe magnetic field, a relative maximum, a relative minimum, etc. of themagnetic-field may be used as a characteristic of the same, that is inany direction or on an absolute-value basis.

Further, in contrast to the preceding description, inferences concerningthe rotation angle may be directly made directly from the outputsignals, with first determining the locus of the magnetic-fieldcharacteristic from the scale, such as, for example, by patternrecognition with respect to the output signals of the sensor elements.For this purpose, the characteristic of the magnetic field along thescale serves only for a better differentiation of the varying outputsignal combinations in the varying rotation angles.

What is claimed is:
 1. An apparatus for detecting a rotation angle of arotation around an axis of rotation, comprising: a transducer magnet forgenerating a magnetic field; a plurality of magnetic-field-sensitivesensor elements for detecting the magnetic field, with the transducermagnet and the plurality of magnetic-field-sensitive sensor elementsbeing arranged such that, when rotating around the axis of rotation, theplurality of magnetic-field-sensitive sensor elements circles around thesame relative to the transducer magnet, and wherein the plurality ofmagnetic-field-sensitive sensor elements define a scale, with thetransducer magnet being arranged such that the generated magnetic fieldcomprises a characteristic at a locus on the scale, and the locus on thescale uniquely depends on the rotary angle at least for a partial areaof a full rotation, wherein the transducer magnet is magnetized inclinedto the axis of rotation.
 2. The apparatus in accordance with claim 1,wherein the transducer magnet is fixedly arranged to the axis ofrotation, and the plurality of magnetic-field-sensitive sensor elementsis fixedly arranged such that the transducer magnet, when rotatingaround the axis of rotation, rotates relative to the plurality ofmagnetic-field-sensitive sensor elements.
 3. The apparatus in accordancewith claim 1, wherein the transducer magnet is of a cylindrical shapeand is magnetized along the surface diagonal, with the symmetry axis ofthe transducer magnet coinciding with the axis of rotation.
 4. Theapparatus in accordance with claim 3, wherein the height and thediameter of the transducer magnet are essentially of the same size. 5.The apparatus in accordance with claim 1, wherein a rotation angle areawithin which the locus uniquely depends on the rotation angle, spans180°.
 6. The apparatus in accordance with o claim 1, further comprising:means for generating a signal indicating a rotation angle partial areaof a plurality of rotation angle partial areas, in which the rotationangle of the rotation is located; and means for receiving the signalindicating the rotation angle partial area, with the rotation anglepartial areas together spanning a rotation angle area of 360°, andwherein a combination of the locus on the scale and the signalindicating the rotation angle partial area uniquely depends on therotation angle.
 7. The apparatus in accordance with claim 1, wherein arotation angle area, for which the locus uniquely depends on therotation angle, spans 360°, the apparatus further comprising: a secondplurality of magnetic-field-sensitive sensor elements offset by rotationaround the axis of rotation relative to the first plurality ofmagnetic-field-sensitive sensor elements, with the generated magneticfield on a second locus on a scale defined by the second plurality ofmagnetic-field-sensitive sensor elements comprises the characteristic,and wherein the combination of the locus on the first scale and thelocus on the second scale being uniquely dependent on the rotationangle.
 8. The apparatus in accordance with claim 1, wherein the sensorelements are arranged on a level spaced from the axis of rotation andwhich is arranged in parallel to the same.
 9. The apparatus inaccordance with claim 1, wherein the plurality ofmagnetic-field-sensitive sensor elements are arranged in the form of atwo-dimensional or one-dimensional array.
 10. The apparatus inaccordance with claim 1, wherein the plurality ofmagnetic-field-sensitive sensor elements are Hall sensors integratedwithin a die.
 11. The apparatus in accordance with claim 1, wherein theplurality of magnetic-field-sensitive sensor elements are arrangedlinear and in parallel to the axis of rotation.
 12. The apparatus inaccordance with claim 1, wherein the characteristic is selected from agroup including a zero crossing, a relative minimum and a relativemaximum of a component of the magnetic field in a predetermineddirection and/or of the magnitude of the magnetic-field.
 13. Theapparatus in accordance with claim 1, wherein the characteristic is thezero crossing of the radial component of the magnetic field, and theplurality of magnetic-field-sensitive sensor elements is arranged todetect the radial component of the magnetic field.
 14. The apparatus inaccordance with claim 1, further comprising: means for inferringconcerning the rotation angle from the magnetic field detected by themagnetic-field-sensitive sensor elements.
 15. The apparatus inaccordance with claim 14, wherein the means for inferring comprises thefollowing: means for determining the locus on the scale from themagnetic field detected by the plurality of magnetic-field-sensitivesensor elements and for inferring concerning the rotation angle from thedetermined locus.
 16. The apparatus in accordance with claim 15, whereinthe means for determining and inferring comprises a means forinterpolating the magnetic field detected by the plurality ofmagnetic-field-sensitive sensor elements, so as to determine the locuson the scale.